So a diamond is essentially worthless, but good upselling makes it worth a lot. This values pays for the processing and marketing of the stone. In the US, for instance, 50 years of brainwashing has made couples forgo homes and food to buy a rock.
In the case of the apparently paid link, they are a delivery service. The problem is that it is hard to create enough value for delivery. Overhead, profits, and minimum wage means that someone is not going to pay a large delivery fee, the value is not going to create a viable business.
Of course you could do what Uber and Lyft does, which is essentially externalize all real costs to contractors, but even in that case profit is apparently not possible without surge pricing which tricks customers into paying multiples of the expected price.